A load targeting tune may run more boost in warmer weather but it will not make more power. It is running more boost to make up for the less dense charge air. Cold weather will always result in better numbers(with everything else being equal.)
What i'm very interested in is where you mentioned GIAC is going to write you a boost targeting tune... that's A LOT of DME logic to change.
"I'm not surprised you get along well with all the other neighbours. If you put fifty children with Down's syndrome in a room there is going to be a lot of hugging." David Thorne